Dylan McStay was playing outside with sisters Megan, 14, and Ruby, 13, in Cwmbran, Wales, when he threw a snowball straight up into the air.
A video shows the moment he watched it come back down and smash into his face - knocking him out cold on the ground.
Mum Georgina McStay, 37, started laughing - until she realised he'd been knocked out.
Thankfully, Dylan was fine – and after a check over from his ambulance worker dad, John McStay, 41, the youngster was back to his normal self.